1. The Field of the Invention
The present invention relates to fluid mixing systems that can be used as a fermentor or bioreactor and, more specifically, fluid mixing systems having a support housing that can be selectively tilted for assembly and/or rocked or otherwise reciprocally moved for mixing fluid.
2. The Relevant Technology
The biopharmaceutical industry uses a broad range of mixing systems for a variety of processes such as in the preparation of media and buffers and in the growing, mixing and suspension of cells and microorganisms. Some conventional mixing systems, including bioreactors and fermentors, comprise a flexible bag disposed within a rigid support housing. A drive shaft projects into the flexible bag and has an impeller mounted thereon. Rotation of the drive shaft and impeller facilitates mixing and/or suspension of the fluid contained within flexible bag.
Depending on the desired processing and batch size, the support housing and the flexible bag contained therein can be relatively tall. Having a tall support housing can produce a number of complications. For example, a tall support housing can preclude passing the support housing through select doorways and thereby limit where the mixing system can be operated. Furthermore, when using tall support housings, it can be difficult to insert the flexible bag into the support housing and adjust the position thereof. This commonly requires the operator to stand on a ladder which can be precarious. In addition, where the mixing system is operating in a room with a relatively low ceiling, a tall support housing can limit the ability to vertically advance a drive shaft down into the flexible bag within the support housing, thereby further limiting where the mixing system can be used.
The impeller is typically fixed at the end of the drive shaft and is designed to remain at a substantially fixed position which is optimal for mixing a narrowly defined volume of solution in the flexible bag. To enable homogeneous mixing of larger volumes of solution, larger bags are used that have an impeller positioned at a location that is optimal for that size of bag.
In some processing procedures it can be desirable to initially mix solutions at a low volume and then progressively increase the volume of the solution. For example, this is a common procedure used with bioreactors for growing cells. The process typically entails dispensing a seed inoculum in a growth media contained within a relatively small bag or container and then transferring the solution to progressively larger bags where additional media is added as the cells grow and multiple. This process is repeated until a final desired volume is achieved. By transferring the solution to different sized bags or containers, which each have a corresponding mixer, the operator can ensure homogeneous mixing of each of the different volumes of solution. Maintaining homogeneous mixing in a bioreactor or fermentor is important to ensure proper feeding and mass transfer of gasses to the cells or microorganisms.
Although the above process of moving solutions to different sized bags to maintain proper mixing and suspension is functional, the procedure has some shortcomings. For example, the necessity of stepping to different sized bags is labor intensive, time consuming, and has high material costs in that each bag is typically discarded after use. Furthermore, transferring between different bags produces some mixing down-time which can influence cell growth. In addition, the necessity of shifting between bags increases the risk of contamination to the solution and potential damage to the cells.
Accordingly, what is needed in the art are methods and/or systems for solving all or at least some of the above problems associated with mixing systems having a tall support housing and/or transferring solutions between multiple different size bags to maintain homogeneous mixing.